with a lot on the line in past debates, romney's done well. >> going up against mitt romney is not a fun thing. he's got the facts. he drills you, stays, tenacious. >> reporter: and sometimes aggressive. >> don't use a term like that. >> reporter: aides admit barack obama in debates can sound like a professorial know it all. >> i understand the broader point that senator clinton has been trying to make over the last several weeks. >> reporter: tonight's format is from 2008, two podiums, moderator jim lehrer, 90 minutes, no breaks. a back-and-forth on domestic issues with possible fireworks. >> i think you're going to see both of them be more aggressive than either of their campaigns have predicted, because the stakes are pretty high. >> reporter: the contest could get even tighter after tonight's clash. but most here in denver agree, this race could be decided by this debate. at the university of denver, i'm steve handelsman, news4. now back to you. >>> you can watch tonight's debate here on nbc 4, live coverage at 9:00. and you can find a watch party by going to our home page on nbc